• A commonly used HTML entity is the non-breaking space:  

A non-breaking space is a space that will not break into a new line.

Two words separated by a non-breaking space will stick together (not break into a new line). This is handy when breaking the words might be disruptive.

Examples:

§ 1010 km/h10 PM

• non-breaking space    
• < less than &lt; &#60;
• > greater than &gt; &#62;
• & ampersand &amp; &#38;
• " double quotation mark &quot; &#34;
• ' single quotation mark &apos; &#39;
• ¢ cent &cent; &#162;
• £ pound &pound; &#163;
• ¥ yen &yen; &#165;
• € euro &euro; &#8364;
• © copyright &copy; &#169;
• ® registered trademark &reg; &#174;
• ™ trademark &trade; &#8482;

Can also be used for accents on letters

• ̀ a a&#768; à
• ́ a a&#769; á
• ̃ a a&#771; ã
• ̀ O O&#768; Ò
• ́ O O&#769; Ó
• ̂ O O&#770; Ô
• ̃ O O&#771; Õ